Paul Ryan's job is to preside over the house and to represent his district. He does not have to bend at the knee to the GOP nominee or the sitting president. We have separation of powers for a reason and at the moment the precedent is being set that if you don't endorse Trump or if you remain neutral in a position of power that you should be destroyed. Donald Trump is not running for king, he is not running for party chairman, he is running for president, and he should not, and his supporters should not, publicly call to destroy someone because they do not bow to Trump. Paul Ryan is not obligated to support Trump and he is not obligated to endorse any candidate even if it weren't Trump. If he does not want to endorse Trump then that should be that, and Trump and his supporters should be mature enough to respect that decision from another voting citizen, even if he is the speaker of the house.